It also frequently happens, and there are many ulti century-long stretches of time in various places in the world from which we have virtually no literature or historical record, not even enough to verify basic facts like what cities were named or where they were located. Sometimes this is because there was virtually nothing being written at the time that anyone thought worth preserving, or because movements, marauders, armies, or some pogrom burned it all and forced people not to discuss the contents on pain of death.
Alarm about the end of civilization is wrong far more often than it is right, but it is eventually right. Societies just recover over time. I'm afraid we've reached the level of technological sophistication that it might be hard to avoid putting a real end to it next time. Our current situation is materially different due to our machines.
